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[en] In pair production, particle and antiparticle are generated when energy form mass and mass form dipole and then separation take place in stronger nuclear filed. After the formation of mass, it goes on oscillation and oscillation causes the dipole creation on mass which further goes on separation from each other as and Q1E3X «Q2E3(X´-X) moreover the forces F32>>F31. These two component play major role for the separation of the masses in oscillation time having frequency (f). Also with the help of size of nucleus and atom, the maximum distance and maximum time for pair production 9.99 x 10-11m and 3.33 x 10-19s, respectively, has been calculated
[en] The effects of nuclear transmutation in zirconium alloys are considered in the paper. The calculated scheme of transmutation of elements in alloys of the system is determined. Numerical estimates of the molybdenum content in zirconium alloys of various compositions were carried out during irradiation in research (SM-3, BOR-60) and power (VVER-1000, PWR) reactors
[ru]В работе рассмотрены эффекты ядерной трансмутации в сплавах циркония. Определена расчетная схема трансмутации элементов в сплавах. Проведены численные оценки содержания молибдена в циркониевых сплавах различных составов при облучении в исследовательских (СМ-3, БОР-60) и энергетических (ВВЭР-1000, PWR) реакторах
[en] Hadronization is known as the nonperturbative part of hadron production process which is described by the process-independent fragmentation functions. These functions refer to the probability densities for the initial partons to fragment into observed hadrons carrying away the momentum fractions of parent partons. In this work, using the quark-diquark approximative model we compute the fragmentation density of gluon into polarized triply heavy baryon Ω in a vector cc-diquark fragmentation. To impose the polarization effect of baryon into the corresponding fragmentation function we shall apply three different scenarios and compare all results.
[en] Shell-model calculations are performed using NuShellX code in the model space π(f5/2,p3/2,p1/2,g9/2)⊗ν(g9/2,g7/2,d5/2,h11/2), which probe the proton core excitation from the interior of Z=38 semiclosed shell and neutron core excitation from the interior of N=56 semiclosed shell for the level structure of 89Sr. Our calculations show that the excitation of a single d5/2 neutron across N=56 semiclosed shell into the h11/2 orbit should have great effects on the excited states of 89Sr. In addition, the systematic features of proton core excitation across Z=38 semiclosed shell into the g9/2 orbit and neutron core excitation across N=56 semiclosed shell into the g7/2,s1/2,d3/2,h11/2 orbits in N=51 isotones are discussed. (author)
[en] Ageing production facilities and low prices of technetium-99m have contributed to a lack of production capacity, which has made supply unreliable. In a new report, the Nuclear Energy Agency (NEA) proposes policy changes that could solve the problem. David Dalton looks at the background and the challenges.
[en] In recent electron-positron angular correlation measurements the observed significant enhancements relative to the internal pair creation at large angles was interpreted as indication of the creation of J=1 boson called X17 particle. In this paper it is brought up that such enhancements can be generated by higher order processes. It is found that nuclear transitions, the transition energy of which is significantly lower than the whole transition energy, can cause peaked angle dependence in electron-positron angular correlation.
[en] The radioisotope production plants aim to select, extract, purify and condition fission product radioisotopes for medical use. 99Mo and 131I are the radioisotopes that are the most widely worldwide produced by fission in nuclear research reactors by irradiation plates made of Al-U. After irradiation, the plates, which contain 99Mo and 131I, are transferred to the radioisotope production plant for separation, conditioning, quality control and dispatch of radioisotopes and radiopharmaceuticals products. Some of these stages take place in an enclosed shielded place called “Hot Cell”. Radioactive gases as iodine and noble gas are emitted in the enclosure. Radioactive iodine can be deposited on the inner side of ventilation pipes. This phenomenon is called plate out.
[en] Make-or-buy decisions represent a critical dilemma faced by many firms. The appropriate decision between designing and manufacturing parts or services in-house, buying them from external providers or combining both is a fundamental firm process. This paper seeks to address this question by updating the traditional make-or-buy literature with new academic insights, developing a make-or-buy framework with a tool for its operationalisation to help managers evaluate sourcing decisions. Design/methodology/approach: First, a literature review of the principal theories and approaches about make-or-buy decisions is discussed. Second, the development of the make-or-buy framework is described and explained based on the results of qualitative interviews with practitioners and a set of interviews of an in-firm case study. Third, the results and the implementation of the framework are outlined. Findings: Our study not only validates the proposed framework through a set of in-firm make-or-buy decisions, but also provides a structure for its implementation and design a decision matrix with a pairwise comparison tool for helping practitioners to put the framework into practice. Research limitations/implications: This paper aims to contribute to the study of the make-or-buy literature in supply chain management through the graphical representation of why and how make-or-buy decisions are made. Interestingly, the paper presents relevant dimensions and factors to be studied and evaluates possible outcomes when approaching make-or-buy decisions. Originality/value: Our results suggest that practitioners should combine this framework with a pairwise comparison matrix and a multi-criteria decision analysis based on the TOPSIS methodology to assess strategic sourcing decisions.
[en] The design of fuel elements shall be such that they satisfactorily withstand the intended irradiation in the reactor core after deterioration processes. Fuel element design shall consider following deterioration factors: external pressure of coolant, additional internal pressure due to fission product within fuel element, irradiation effect of fuel and other materials in fuel assembly, pressure and temperature change induced by power change, chemical effect, static load, dynamic load by flow induced vibration and mechanics vibration, heat transfer behaviour change induced by deformation and chemical effect. Margins shall be taken account for uncertain factors of data, calculation, and fabrication. Fuel design limit including permitted fission product release rate shall not be exceeded in normal operation, AOO transient shall not lead to significant deterioration of fuel element, fission product release shall be kept to a minimum. Design of fuel assembly shall provide convenience for inspection of fuel structure and component. During accident condition, fuel element shall remain in position, the deformation shall not reach the extent that would prevent sufficient post-accident core cooling, and specified limits shall not be exceeded.
[en] One of the major concerns with the continued growth of the nuclear power industry is the production of the high level radioactive wastes which are by-products of the fission process. The risks associated with the disposal of high level wastes derive from the potential for release of radioactive materials into the environment. The assessment of these risks requires a methodology for risk analysis, an identification of the radioactive sources, and a method by which to express the relative hazard of the various radio nuclides that comprise the high level waste. Radioactive wastes are either contained or discharged. Contained wastes are either stored or disposed of in trenches, caverns, or deep mines. On the other hand, some gaseous and liquid wastes are discharged from chimney stacks or sea pipelines directly into the environment. Contained wastes either decay before escaping from their disposal site or are arranged to leak at such a low rate as not to raise appreciably the level of radiation in the environment. In the multiple barrier approach, each containment is a reliable barrier to migration-the packaging material (glass or concrete), the vault and backfill, and the geology. (author)